The present invention relates to a sorting system for flat mail items with a number of sorting registers and at least one storage module, with the sorting registers and the at least one storage module being connected to a sorting circuit via switch points.
With today's mail sorting systems in some case very large volumes of mail items must be sorted and distributed at mail sorting centers and/or larger post offices. Thus for example the average daily volume of mail in Germany amounts to around 80 million letters which have to reach their addressees the day after being mailed or at the latest two days after being mailed. Such mail items are generally referred to by the generic term of letters. Such letters are identified by their length and their width generally being large in relation to their height. However, as regards the definitive dimensions for the assignment of the mail items to this “letters” group there are significant differences between the mail administrations of the various national states. As well as these deviations in size, it is easy to see that the nature of the mail items, even if they are all “letters,” differs significantly under some circumstances.
It is thus easy to imagine that the processes of mail automation must be operated nowadays with high levels of efficiency and as a result of cost pressures also with a comparatively small number of operators. To achieve sufficiently high throughput rates in the sorting systems the mail items are conveyed through the sorting system at speeds of up to 4 m/s or in places at even greater speeds, and are sorted to their destination by appropriate switch point settings and a clever, generally multistage delivery round sorting system.
For rough and fine sorting of the mail items a number of sorting registers are thus connected via the switch points to the sorting circuit. In such cases each sorting register as a rule has a number of destinations which is generally at least in the double-digit range, to which the mail items destined for them are likewise directed by corresponding switch point settings. It is easy to see here that the switch points are only able to be switched using a certain time constant and that the mail items in the mail item stream must thus be at a specific distance from each other, to allow the switching processes for the switch points in precisely the intervals made possible by the minimum gap. At a speed of conveyance of around 4 m/s and a minimum distance of 70 mm for example this time window for switching a switch point amounts to just 17.5 1 ms. Because of the short intervals, mail items which are not at the required minimum distance from the previous item must be extracted from the stream of mail items in order to create the required gaps. This likewise applies to mail items which are fed to a sorting register of which the function is disturbed because of a blockage or as a result of a compartment overflow. So that the entire sorting process does not have to be halted, the mail items destined for the faulty sorting register are also extracted from the stream of mail items.
In the prior art these mail items had to be taken back manually to the so-called feeder and then had to be introduced there back into the sort circuit by reentering their destination address.